The present invention relates to a synchronizing system for signal pulses transmitted between a key service unit and a key telephone set in a key telephone system which is designed so that key information or the like is transmitted by a time division manner between the key service unit and the key telephone set.
A conventional synchronizing system employs a synchronizing signal channel separately provided of a data signal channel. Further, such a system has also been proposed that in case of using the same channel in common to the two kinds of signals, different codes are used for them, respectively. With the prior art systems, however, an extra cable pair is needed and, in case of multiplex transmission using the same cable, a MODEM or code detector is required, resulting in the defect of complex arrangements.